DE102015205238B4 - A printer having a system for detecting inoperative ink jets in printheads that eject clear material using a translucent substrate - Google Patents

Abstract

A printer for forming objects, comprising:a planar substrate (308) having a surface and at least one edge along a perimeter of the substrate;a printhead (22, 26) configured to eject material onto the surface of the substrate;a light source (314 ), arranged to radiate light into the at least one edge of the substrate;an optical sensor (304) arranged to receive light emitted from the surface of the substrate, the optical sensor (304) being configured such that it can generate image data corresponding to the surface of the substrate; anda controller (324) operatively connected to the printhead (22, 26), the light source (314) and the optical sensor, the controller (324) being configured to actuate the printhead (22, 26), to eject material onto the surface of the substrate in a predetermined pattern, selectively activating the light source (314) to receive image data generated by the optical sensor while the light source (314) projects light into the edge of the substrate and that it detects inoperative ink jets in the print head (22, 26) in relation to the received image data and the specified pattern, the flat substrate (308) being translucent and providing total reflection of the light entering the flat substrate (308). 308) occurs along the at least one edge of the flat substrate (308).

Description

TECHNICAL FIELD

The apparatus disclosed in this document relates to printers that produce three-dimensional objects and, more particularly, to detecting inoperative ink jets in such printers.

BACKGROUND

Printing documents on substrates such as paper is well known. Newer forms of printing now include three-dimensional digital manufacturing, also known as digital generative manufacturing. This type of printing is a process of creating a three-dimensional, solid object of essentially any shape from a digital model. Three-dimensional printing is a generative process in which one or more print heads sequentially eject layers of material onto a substrate in various shapes. Three-dimensional printing is distinct from traditional object-forming techniques, which essentially rely on removing material from a workpiece through a subtractive process such as milling or drilling.

Producing a three-dimensional object with these printers can take hours or even days for some objects. One problem that arises when producing three-dimensional objects with a 3D printer is persistent functionality of the ink jets in the print heads that eject the droplets of material that form the objects. While printing an object, one or more ink jets may degrade, ejecting the material at an angle to the printhead instead of the normal orientation, ejecting drops that are smaller than an ink jet should eject, or ejecting no drops at all . An inkjet with any of these malfunctions is known as a dead inkjet. The same weaknesses are known for print heads in document printing with print heads. If the operating status of one or more ink jets deteriorates during printing of a three-dimensional object, the quality of the print head cannot be evaluated until printing is completed. Accordingly, print jobs that require many hours or several days can produce objects that do not meet specifications due to inoperative printheads. When such objects are detected, the printed objects are discarded, restorative procedures are applied to the printheads to restore inkjet functionality, and the print job is repeated. Even when printing documents at high speeds on a moving web, unacceptable images can be produced over a long stretch of the web and this portion of the web may need to be discarded.

Although systems in document printing systems have been developed to detect dead inkjets, detecting dead inkjets in commercial printing systems is more problematic. In particular, the use of clear materials and inks are problematic in both object printing and document printing systems. These materials and inks are difficult to detect by imaging systems because the contrast between clear inks/materials on the substrates onto which they are ejected is low. Accordingly, the noise of the image data of the patterns on the substrate makes the analysis of the test patterns difficult. An apparatus that enables the detection of inoperative ink jets during printing with clear ink or materials would enable restorative processes to be applied during object printing so that a properly formed object or document can be produced. In this way, the printer's product yield is improved and printing is more economical.

US 2010/ 0 121 476 A1 describes a method and system for the three-dimensional production of an object. The method includes: forming a plurality of layers in a configured pattern that corresponds to the shape of the three-dimensional object, wherein at least one layer of the plurality of layers is formed with a predetermined and different thickness to compensate for the shrinkage of the layer in the vertical direction. In various exemplary embodiments of the invention, the spread of build material of one or more layers is at least locally thinned to maintain a predetermined thickness and a predetermined planar resolution for the layer.

JP 2009-220 394A describes an ink jet discharge inspection apparatus. The apparatus performs preliminary ink discharge from the discharge nozzles of an ink jet recording apparatus simultaneously with the discharge inspection, and includes a head unit having one or more ink jet heads, a discharge inspection recording medium, and an image preparation mechanism for controlling the ink to be pre-discharged and controlling discharging onto a recording medium as an inspection image, an image information acquiring section for optically acquiring the inspection image recorded on the recording medium, an image information processing section for analyzing and checking differences, and the like ities of the captured image information and reference image information by comparison, as well as a control section to control the actions of the sections.

Summary of the invention

It is the aim of the present invention to improve a system for detecting inoperative ink jets in printheads. This object is achieved by a printer for forming objects according to claim 1. Embodiments of the invention are set out in the dependent claims.

BRIEF DESCRIPTION OF DRAWINGS

• 1 ist eine perspektivische Ansicht eines 3D-Objektdruckers.
• 2 ist eine Frontalansicht eines 3D-Objektdruckers mit einem Gehäuse, das einen Raum in dem Gehäuse für ein Modul darstellt, das eine Erkennung funktionsloser Tintenstrahlen in dem Druckkopf während einer Druckoperation ermöglicht.
• 3 ist eine perspektivische Ansicht eines Moduls zur Erkennung funktionsloser Tintenstrahlen, das in den in 2 gezeigten Raum passt.
• 4 ist ein Flussdiagramm eines Verfahrens zum Betätigen des Moduls aus 3.

The foregoing aspects as well as other functions of an apparatus or printer that detects inoperative ink jets during three-dimensional printing are explained in the following description in conjunction with the accompanying drawings.

• 1 is a perspective view of a 3D object printer.
• 2 is a front view of a 3D object printer with a housing, illustrating a space in the housing for a module that enables detection of inoperative ink jets in the printhead during a printing operation.
• 3 is a perspective view of a non-functioning inkjet detection module shown in Figures 1 2 shown space fits.
• 4 is a flowchart of a method for operating the module 3 .

DETAILED DESCRIPTION

For a general understanding of the environment for the device disclosed herein, as well as the details for the device, reference is made to the drawings. In the drawings, similar reference numbers indicate similar elements.

1 shows a configuration of components in a printer 100 that produces a three-dimensional object or part 10. As used herein, the term “3D printer” refers to any device that ejects material associated with image data of an object to form a three-dimensional object. The printer 100 includes a substrate supply 14, a material supply 18, a pair of inkjet printheads 22, 26, a building substrate 30, a flat support element 34, a columnar support element 38, an actuator 42 and a controller 46. Line 50 connects printhead 22 with the substrate supply 14 and line 54 connects printhead 26 to material supply 18. Both inkjet printheads are operated by the controller 46 in connection with three-dimensional image data in a memory which is operatively connected to the controller to eject substrate and material, which be provided to the respective print head. The material forms the structure of the part 10 to be manufactured, while the support structure 58 formed from the support material allows the material to retain its shape while the material hardens while the part is constructed. When the part is hardened, the support structure 58 is removed by washing, blowing or melting.

The controller 46 is also operatively connected to at least one, and possibly more, actuators for controlling movement of the planar support member 34, the columnar support member 38, and the printheads 22, 26 relative to one another. That is, one or more actuators may be operatively connected to a structure of the printheads to move the printheads in a process direction and a cross-process direction with respect to the surface of the planar support member. Alternatively, one or more actuators may be operatively connected to the planar support member 34 or the columnar support member 38 to move the surface on which the part is manufactured in the process direction and in a cross-process direction. As used herein, the term “process direction” refers to movement along an axis in the surface of the planar support member 34, and “cross-process direction” refers to movement along an axis in the planar support member surface that is perpendicular to the process direction axis therein surface stands. These directions are marked with the letters “P” and “CP”. 1 designated. The print heads 22, 26 and the columnar support member 38 are equipped with an actuator for moving in a direction perpendicular to the flat support member 34. This direction is referred to in this document as the vertical direction and is indicated by the letter “V”. 1 marked. Movement in the vertical direction may be achieved by one or more actuators operatively connected to the columnar support member 38, by one or more actuators operatively connected to the printheads 22, 26, or by one or more actuators both are connected to the columnar support element 38 as well as the print heads 22, 26. These actuators in these various configurations are operatively connected to the controller 46, which actuates the actuators to vertically move the columnar member 38, the printheads 22, 26, or both.

A 3D object printer with a housing is in 2 shown. Printer 60 has a housing 64. Within the housing 64 are six compartments that are generally cubic in shape. The housing 64 is in 2 shown without the doors, which close to conceal the compartments. Compartment 72 includes a planar support 78 on a movable platform 82. The movable platform 82 is equipped with one or more actuators and guide members (not shown) to enable the movable platform 82 to move up and down in a vertical direction. The planar support 78 is the surface on which a three-dimensional object is formed. In some embodiments, printhead 86 has a length approximately equal to the length of planar support 78 toward the rear wall of tray 72 to the opening at the front of the tray. In these embodiments, the printhead 86 is mounted on the support member 92 in the space between the side walls 96 and 100 of the housing 64 to allow only linear reciprocating movement. In other embodiments, printhead 86 has a length that is less than the length of planar support 78 toward the rear wall of tray 72 to the opening at the front of the tray. In these embodiments, the printhead 86 is mounted on support member 92 in the space between the side walls 96 and 100 of the housing 64 to permit reciprocating movement in two mutually perpendicular directions in a plane above compartment 72. In these various embodiments, one or more actuators 104 are operatively connected to the printhead 86. The controller 108 actuates the actuators 104 to either linearly move the printhead 86 back and forth on the support member 92 or to move the printhead in two mutually perpendicular directions in a plane. By selectively actuating the ink jets in the printhead 86 and vertically moving the support platform 82 and horizontally moving the printhead 86 on the member 92, a three-dimensional object can be formed on the planar support 78.

The in 2 Area 112 shown in dashed lines indicates the arrangement of a module that uses a translucent substrate to detect inoperative ink jets in the printer 60. As mentioned above, if an inkjet fails during an object printing, either by completely or partially failing to eject material, or by incorrectly ejecting material in a distorted direction, the object so produced will have a defective shape. Currently, this defective shape cannot be detected until the object is manufactured. Using the area 112 for optically scanning material being ejected onto a translucent substrate, the printer 60 may be designed to detect inoperative ink jets during object manufacturing, as described in more detail below. Some components in the module 300 are movable in the horizontal direction H, the depth direction D, and the vertical direction V, as shown in the figure.

An embodiment of a module that detects inoperative ink jets during object printing is shown in the block diagram of 3 shown. The module 300 is set up to fit into an area 112 of the printer 60. The module 300 includes an optical sensor 304, a translucent substrate 308, a substrate transport 312, a light source 314, one or more actuators 316, a cleaning element 320, a controller 324 and a waste container 328. The optical sensor is for bidirectional movement in both directions W and L designed by an actuator 316. This allows the optical sensor 304 to move across the surface of an endless belt 330 of transport 312. The transport 312 includes the endless belt 330, which is coupled around the rollers 332. An actuator 316 drives the rollers 332 to bidirectionally rotate the belt to move the substrate 308 to a position where it can be printed and then to a position where it can be cleaned. The controller 324 is operatively connected to the actuators 316 to move the optical sensor 304, to drive the rollers 332 to move the translucent substrate 308 with the belt 312, and to clean the translucent substrate 308 with the cleaning member 320. In some embodiments, the optical sensor 304 only needs to be designed for bidirectional movement in the L direction, provided the sensor is at least the width of the substrate 308.

The translucent substrate 308 is a planar element of material that supports the material and substrate ejected from the printhead 86 and that provides total reflection of light entering along an edge of the substrate. These materials allow light entering along an edge of the substrate to remain within the planar substrate unless any material on the surface of the substrate changes the total internal reflection property at the interface between the material and the planar surface. For printers that eject materials or ink with a refractive index in a range of about 1.3 to about 1.5, the translucent substrate typically has a refractive index in a range of about 1.4 to about 1.8. The flat substrate can, for example, consist essentially of polycarbonate, acrylic or glass. When the substrate is printed, the similar refractive index of ejected material allows on the flat surface of the substrate as well as the Substrate that light that propagates in the substrate enters the material despite the shallow angle of incidence with respect to the substrate-material interface. The light in the material has a steep angle of incidence relative to the interior surfaces of the material on the substrate, allowing light to escape into the surrounding air. Other parts of the light experience numerous internal reflections before finally emerging from the material. The escaping light provides a visual indication of the position of the material on the flat surface of the translucent substrate, as the light escaping from the material piles is in marked contrast to the uncovered surface where the light is not escaping. When the sensor 304 is moved over the substrate 308, the sensor 304 generates electrical signals that form image data of the test pattern on the substrate 308.

In 4 A method of operating a printer that produces three-dimensional objects is shown. In the description of this method, statements that a process performs a task or function refer to a controller or general-purpose processor executing programmed instructions stored in a memory operatively connected to the controller or processor to process data or a or to operate multiple components in the printer to perform the task or function. The controller 324 mentioned above may be such a controller or processor. Alternatively, the controller 324 may be equipped with more than one processor and associated circuitry and components, each capable of performing one or more tasks or functions described herein.

At specified times during printing operation, the controller 108 ( 2 ) an actuator 104 to move the printhead 86 into the module 300 located in the area 112 (block 404). In response to controller 324 detecting the printhead in module 300, controller 324 actuates transport 312 to move translucent substrate 308 to a position opposite printhead 86 (block 408). Controller 324 then generates a signal to controller 108 to actuate the ink jets in the printhead to print a test pattern onto substrate 308 (block 412). In one embodiment, each ink jet in the printhead is repeatedly actuated to form a pile of material, also referred to as a test spot, on a portion of the substrate 308 opposite the ink jet. When the test pattern is printed, controller 108 moves the print head out of module 300 and generates a signal to controller 324. In response to the signal from controller 108, controller 324 actuates an actuator 316 to move optical sensor 304 to a position opposite Move test pattern on substrate 308 (block 416). This movement can be accomplished by moving the optical sensor to the location where the substrate 308 was printed or by operating the actuator drive rollers 332 to move the substrate to the location where the optical sensor is located. The controller 324 then activates the light source 314 to radiate light into an edge of the substrate 308 (block 418). In the figure, the light source radiates light that propagates in the L direction into the edge of the substrate 308 at the right edge as shown in the figure, although the light may also be radiated into any of the three other edges. The light source 314 may be an array of light-emitting diodes (LEDs), an array of laser diodes, a cold cathode fluorescent tube, a filament, or the like. These arrays can be one-dimensional, ie linear, or two-dimensional arrays. The light generated by light source 314 may be infrared, ultraviolet, polychromatic, or monochromatic. The light source may be separate from the substrate or attached to the substrate to allow the light to be irradiated into the substrate. The process continues by actuating an actuator to move the optical sensor 304 in the L direction across the substrate 308 to generate electrical signals that are provided to the controller 324 as image data of the flat surface of the substrate 308 (block 420). . The areas where the material and substrate have been ejected emit light, as explained above. The proportions of the surface with total reflection of light and the proportions that emit light should correspond to the test pattern used to eject material and substrate. The flat surface image data is analyzed with respect to the expected positions for the material and substrate used to form the test pattern for identifying non-functional ink jets (block 424), and if non-functional ink jets are identified, a signal is sent to the operator of the Printer generated indicating a defective printhead (block 428). The operator can then take appropriate action. Once the substrate has been imaged at the position where it was printed, the process continues with the controller 324 actuating the actuator 316 to reverse the transport 312 and return the substrate to its home position (block 432). Otherwise the substrate is already in the cleaning position. Controller 324 actuates an actuator 316 to engage the substrate 308 into the cleaning element 320 and then move the cleaning element 320 in the L direction to remove material from the substrate (block 436). The removed material is collected in the waste container 328, shown in the figure as being located at the front end of the endless belt 330, although Other positions and directions of movement of the cleaning element can also be used. The tray 328 may be removed from the printer from time to time and either replaced or emptied and then reinstalled. When the substrate has been imaged at the position at which it was printed, the controller 324 actuates the actuator 316 to return the optical sensor 304 to the position above the substrate 308 (block 440).

The process of 4 continues with an evaluation of substrate cleaning in some embodiments. In these embodiments, after the cleaner removes material from the surface of the substrate (block 444), the controller activates a light source and moves the optical sensor across the substrate to generate image data of the cleaned substrate (block 448). This image data is compared to a specified threshold to identify whether light emitted from the substrate exceeds the threshold because light is only emitted when material is on the surface of the substrate (block 452). If the limit is exceeded, there is noise in the image data received from the optical sensor. In response to this noise, another cleaning operation may be performed (blocks 436-440) and another cleaning evaluation occurs (blocks 444-452). If the substrate has been cleaned more than once in the current test (block 456), the image data from at least a portion of the substrate is stored in a memory operatively connected to the controller (460). This noise data is subtracted from image data obtained during the next test of the printhead to allow identification of the test pattern without interference from the noise so that the controller can detect inoperative ink jets.

The cleaning element 320 is mounted on a support element 348 which is operatively connected to an actuator 316. As mentioned above, the controller 324 actuates the actuator to move the support member and clean the substrate 308 with the cleaning member 320. This action reverses material and substrate from the substrate 308 into the waste container 328 to renew the surface of the substrate for printing another test pattern. The cleaning element 320 may include a supply of cleaning solution 340 configured to distribute cleaning solution on the substrate before the cleaning element sweeps the substrate. The cleaning solution acts chemically on the material and carrier material to dissolve the material before it comes into contact with the cleaning element. Together or alternatively, a heater 344 may be operatively connected to the controller to selectively connect the heater to a power supply. The heater is positioned relative to the cleaning element 320 to heat material and substrate before the cleaning element sweeps the substrate 308.

Although the embodiments discussed above are in a printer that forms three-dimensional objects, a translucent substrate and the system that detects inoperative ink jets based on the light such a substrate emits may also be used in 2D document printing systems, particularly those that use clear inks. Thus, as used in this document, the word "material" refers to substances that can be used to form three-dimensional objects as well as inks that are used for document printing. In document printing systems, a translucent substrate may be positioned adjacent a print area in the printer and from time to time the print head is moved relative to the substrate to eject ink onto the substrate. Light is then irradiated into the substrate and the substrate is imaged so that the image data can be analyzed to identify nonfunctional inkjets. Likewise, printheads that eject clear ink onto a movable web or imaging element, such as a roller, can be moved relative to a translucent substrate for printing and detecting inoperative ink jets.

Claims (10)

A printer for forming objects, comprising: a planar substrate (308) having a surface and at least one edge along a perimeter of the substrate; a print head (22, 26) designed to eject material onto the surface of the substrate; a light source (314) arranged to radiate light into the at least one edge of the substrate; an optical sensor (304) arranged to receive light emitted from the surface of the substrate, the optical sensor (304) configured to generate image data corresponding to the surface of the substrate; and a controller (324) operatively connected to the printhead (22, 26), the light source (314) and the optical sensor, the controller (324) being configured to actuate the printhead (22, 26). to eject material onto the surface of the substrate in a predetermined pattern, selectively activating the light source (314) to receive image data generated by the optical sensor while the Light source (314) has irradiated light into the edge of the substrate, and that it detects inoperative ink jets in the print head (22, 26) in relation to the received image data and the specified pattern, the flat substrate (308) being translucent and a total internal reflection of the light entering the flat substrate (308) along the at least one edge of the flat substrate (308). printer Claim 1 , wherein the optical sensor (304) further comprises: a one-dimensional array of photodetectors. printer Claim 1 , wherein the optical sensor (304) further comprises: a two-dimensional array of photodetectors. printer Claim 1 , further comprising: a cleaning device configured to remove material from at least a portion of the surface of the substrate; and the controller (324) operatively connected to the cleaning device, the controller (324) being further configured to actuate the cleaning device to remove material from the at least a portion of the surface of the substrate. printer Claim 4 , whereby the controller (324) is still designed in this way; activating the light source (314) after the cleaning device removes the material from the surface of the substrate and identifying noise in the image data received from the optical sensor. printer Claim 5 , wherein the controller (324) is further configured to actuate the cleaning device to remove material from the flat substrate (308) in response to the identified noise in the image data that exceeds a specified threshold. printer Claim 6 , wherein the controller (324) is further configured to store in a memory operatively connected to the controller (324) at least a portion of the image data used to identify the noise and inoperative ink jets in relation to detect at least a portion of the image data that was used to identify the noise stored in the memory. printer Claim 4 , wherein the cleaning device further comprises: an element configured to engage and move with respect to the at least a portion of the surface of the substrate; and an actuator operatively connected to the element and the controller (324) to enable the controller (324) to actuate the actuator to move the element with respect to the at least a portion of the surface of the substrate. printer Claim 4 , wherein the cleaning device further comprises: an applicator operatively connected to a supply of solvent; and the controller (324) further configured to actuate the applicator to apply solvent to the at least a portion of the surface of the substrate to remove material from the at least a portion of the surface of the substrate. printer Claim 4 , wherein the cleaning device further comprises: a heater arranged to heat the at least a portion of the surface of the substrate; and the controller (324) further configured to actuate the heater to heat the at least a portion of the surface of the substrate to remove material from the at least a portion of the surface of the substrate.

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